The use of intra-aortic balloon (IAB) assemblies for assisting the pumping action of the heart are well-known. Recently, research efforts have placed emphasis upon facilitating the insertion and placement of such balloon assemblies. One of the major objectives is to obtain reductions in balloon profile, i.e. outer diameter, in order to achieve the aforementioned results. Early efforts to achieve such results led to the technique of evacuating the balloon and wrapping the evacuated balloon about an elongated member substantially coaxial with the longitudinal axis of the balloon. This technique is disclosed in U.S. Pat. No. 3,939,820 issued on Feb. 24, 1976 to Grayzel, et al. Another technique comprised the evacuation of an IAB identified as the "PHASIC" balloon designed by the present inventor and inserted into a cannula grafted to a patient which balloon folded over itself upon insertion. Another technique adopted to achieve substantially similar results utilizes a twistable, elongated stylet coaxial with the longitudinal axis of the balloon, one end of the balloon being rotatable relative to the opposing end, and being twisted about the stylus in order to reduce the balloon profile. This technique is disclosed in U.S. Pat. No. 4,261,339 issued Apr. 14, 1981 in the name of Hanson, et al. A novel improvement on this technique is disclosed in application Ser. No. 253,680, filed Apr. 13, 1981 in the name of the inventor of the present invention, and disclosing an intra-aortic balloon assembly having a stylet rotatable through a manually operable control knob arranged remote from the balloon, for wrapping the balloon.
The balloons of the above techniques which employ a flexible stylet may be introduced into the body through a percutaneous technique such as, for example, the Seldinger technique, wherein an introducer sheath is initially introduced into the body and the balloon is thereafter introduced into the body by insertion into and through said introducer sheath, which may then be either partially or totally removed after the balloon has been properly placed.
Still another technique for reducing the profile of the balloon but without either wrapping or twisting, is disclosed in U.S. Pat. No. 4,327,709 issued on May 4, 1982, the Hanson, et al., and describing a technique in which the balloon is evacuated. Hanson alleges that the balloon membrane forms a flat tape-like cross-section with the stylet lying along the central axis thereof. Hanson further alleges that the two halves of the balloon lying on either side of the stylus are folded over to form first and second longitudinal folds. The balloon is thereafter inserted into one end of the insertion sheath used in the performance of the Seldinger technique. This technique assumes that the balloon will fold in the alleged manner and that it form a sufficient number of longitudinal folds to enable its insertion into the insertion sheath.
Although all of the above-mentioned techniques tend to reduce the profile of the balloon, they nevertheless exhibit certain disadvantages. For example, the balloon assemblies which rely upon twisting techniques create a large number of folds to generate a non-uniform helical pattern which may damage the introducer sheath and/or the patient or the balloon itself, which is greatly stressed by such wrapping. The balloon assemblies adapted for folding and/or wrapping techniques also create a large number of folds, due to their geometry and thus all of the above techniques fall short of reaching a minimal outer profile and without introducing additional disadvantages. In addition thereto, none of the above techniques teach a pre-wrapped balloon, or a method or means for maintaining a pre-wrapped balloon in the fully and tightly wrapped state, until it is ready for insertion and without stressing the membrane.
In an effort to overcome the disadvantages of the above-mentioned prior art, the inventor of the present invention has developed an intra-aortic balloon adapted for percutaneous insertion and a method for insertion of same which apparatus and method is set forth in copending application Ser. No. 442,958 filed Nov. 19, 1982. The intra-aortic balloon assembly described in the aforementioned copending application comprises a balloon having its distal end terminating in a tip and having its proximal end joined and communicating with the distal end of an elongated catheter tube. A flexible, slender stylet extends rearwardly from the tip of the balloon and into the catheter tube. The ends of the balloon respectively joining the tip and catheter tube are each displaced from the longitudinal axis of the balloon to position the stylet along an imaginary line which is displaced a substantial distance from the longitudinal axis of the balloon, when inflated, so that the stylet preferably rests against or is in close proximity to the interior surface of the balloon along the entire length thereof. The adjusted position of the balloon axis relative to the stylet enables the balloon to be wrapped more tightly and more easily than any of the conventional designs.
Wrapping is accomplished by evacuating the balloon so that it forms a flat, tape-like cross section. However, contrary to conventional designs, the stylet rests against the interior surface of one of the folds of the flattened balloon, enabling the balloon to be wrapped about the stylet in a single, continuous, tight spiral, in much the same way that a flag is wrapped about a flagpole.
The intra-aortic balloon design of the above-mentioned copending application utilizes a stylet which extends through the offset balloon and catheter and extends into a luer which is coupled to a rotatable, manually operable control knob to permit twisting or rotation of the stylet to compensate for any undesired twisting which may result from the wrapping operation.
Once the offset balloon is tightly wrapped about the stylet, the balloon is maintained in the fully wrapped position by means of holder halves which are releaseably joined to one another to encircle the wrapped balloon and thereby retain the balloon in the tightly wrapped condition. The interior surfaces of the holder halves are preferably either formed of or coated with a low friction surface which permits the balloon to be easily pushed out of the holder assembly and into the insertion sheath. The holder halves are joined to one another by plastic strips of tape which are wrapped about the holder halves and adhesively joined thereto, the tape strips being easily cut away when it is desired to remove the holder halves from the intra-aortic balloon assembly. The interfitting of the holder halves by tongue and groove joints permit the tape strips to be severed by a sharp instrument without any danger of accidently cutting the balloon.
During insertion, the balloon experiences lateral folding as it is pushed through the sheath during balloon insertion or as it is pulled from an artery during balloon removal. This may cause serious injury to the patient.